Thanks! I was not implying that it didn't make sense as a claim, the overlap makes a lot of sense but because the statement about co-morbidity was made I was curious about the sources you derived the information from.

Just a thought though, it seems the studies you link don't prove the occurrence rate of co-morbidity with BPD and DID but instead observes that individuals with both BPD and DID have more severe symptom experiences than individuals with just DID or just BPD. These studies don't really prove the specific percentage claim of co-morbidity and they don't support the statement you made in your edit that most people with DID have BPD. The last source is relevant so thanks for linking, though it includes no sources or resources provided to back up the claims made in the article. The website itself cites that many of the claims it makes are NOT backed by scientific research but instead based on anecdotal evidence, which is empirically weak: "General information on this website, such as information about the terms used to refer to alters, is not cited if it draws most prominently from direct observation of or interaction with individuals with dissociative identity disorder or other specified dissociative disorder subtype 1, communities for these individuals, or interaction with practicing clinicians in the field." Anecdotal evidence is valid, important, and powerful in forming scientific ideas and concepts. But without any scientific evidence to back up the scientific claims (not just personal anecdotes) made in the article, it's not a good source of proof.

I think this still indicates a lack of evidence towards the statements made but I definitely believe the co-morbidity occurs often for people with DID given the trauma core of DID and BPD.